1. Field of the Invention
The invention is directed to a constructional unit including an electric machine with a stator and with a rotatable rotor, a rotatable output element that operatively communicates with the rotor to transmit torque, and an offset arrangement.
2. Description of the Prior Art
A generic constructional unit of the type mentioned above is disclosed in DE 10 2006 053 660 A1 and has an electric machine, torsion damper, and internal combustion engine that is separably operatively connected to the rotor of the electric machine via a clutch disk. due to tolerances in manufacture and assembly and due to wobbling movements of the crankshaft, axial offsets as well as angular offsets occur between the rotational axes of the various modules in the powertrain, for example, the rotational axis of a crankshaft of the internal combustion engine, a rotational axis of the rotor of the electric machine, a transmission input shaft of a shift transmission, etc. These offsets between the individual shafts of the modules are compensated in the above-cited disclosure through an offset device, particularly a wobble-absorbing bearing support of the rotor relative to the stator, and a variety of bearing variants for the arrangement of the rotor at the stator are described. With present-day offsets of 1 mm and more, this wobble-absorbing bearing support is exposed to very high loads, which has a negative influence on the electric machine.
It should be noted that the offsets are not compensated or eliminated; rather, torque transfer is simply enabled between two rotatable component parts whose rotational axes are misaligned.
A further possibility for implementing torque transmission in case of offset is shown in DE 100 02 830 B4 with respect to an independent clutch disk which, however, is not a constructional unit of the generic type mentioned above. In this case, a driver disk is operatively connected to a hub disk via teeth with the intermediary of coil springs so as to form a shaft offset arrangement. The teeth offer sufficient backlash in radial direction and circumferential direction so that the driver disk and hub disk can have different axes of rotation to a certain extent but are nevertheless torque-transmittingly connected via the coil springs.
In hybrid vehicles and electric vehicles, electric machines are used as drive motors or are integrated within the powertrain to assist a main drive. Therefore, as a result of the modular type of construction, there are usually a plurality of modules lined up in the powertrain. Requirements respecting manufacturing tolerances and assembly tolerances must be strict to prevent shaft offsets between the modules. These offsets can be eliminated at high expenditure, for example, through high-precision manufacture and corresponding arrangements for centering and bearing support, which align the modules with respect to one another, for example, pilot bearings. This requires corresponding additional installation space.